Evening star. [volume] (Washington, D.C.) 1854-1972, 1887-10-06

Neulehatel Rock, :l,es9 ool5 ool6
Grahanite, 53,l12 O.02O
From this table it Will be seen that as the record
stands now, even the vulcanite pavement is some
what more expensive to maintain than the
asphalt pavementS.
THE PROBLEM OF STREET GRADES
The ''many perplexing problems in the grades Of
streets" upon which bituminOus bases have been
laid result from the fact that the three courses Of
distillate pavements, the base the binder and the
wearing surface coalesce so as to form solid mass
6 inches In thickness. The wear on the surface is
becomes exposed On the most travelled part OF the
street, the pavement near the gutter may be worn
OF the Old surface should be removed and the new
surface, ~ inches thick, laid directly upon the
binder. IL Is however, impracticaDe to strip a
cOal-tar surface. II may be broken by the pick
and bar, but IL breaks readily in the base or
binder, as at the original line OF dcmarcatiOn In
fact there is no such line. The practice Is to cut
out what may be necessary near the curb and put
a new surface on the roadway as IT stands. The
result Is TO raise the level OF the roadway at every
resurfacng or II the original level at the curb be
maintained by the method OF cutting out as stated
to increase the crown OF the street; but as such
pavementS Will not, as rule, require resurfaCing
at more frequent intervals than every fifteen
years, and each reSurfac1ng should not raise the
level more than One-half inch, the upward growth
will not exceed and bird inches per century
The asphalt pavement on a hydraulic base Is
free from this evil. There is little cohesion be.
tween the base and the surface, and the latter Is
easily StIlppcu. Ills ID uOt WITHOUT
| its corresponding defect. The lack OF cohesion
| diminishes the longitudinal strength, and the
| asphalt Is In some cases pushed, pulled, OF
stretched by trafflc into a wavelike surface, dis
agreeable TO travel, and requiring repairs which
| otherwise would De unnecessary. 1t is possible
that this defect may be caused TO some extent by
| the depth Of the asphalt mixture c2& 1nches).
SO far as Capt. Griffin's observations extend thu
dlstillate pavementS are freer from the defects O
| wave surfaces and weather cracks than tn,
asphalt The conditions affecting the durabilit,
OF pavements are quite peculiar In this city. Pave
broad streets and light traffic, may be quite un
suited to other cities. On the other hand pave
ments OF the strength and durability requisite TO
| other cities may be unnecessarily expensive 70
| washington. Climate Is very important elemen
10 consider In the selection OF the most durable
| pest pavement. Our pavementS suffer more dur
Ing the three months OF winter than during tn
| remaining nine months OF the year. For fifteel
years some OF the distillate pavements have stOO,
| the test OF service and though may have failed
| the record OF the vulcanite and Scharf show tina
| such payementS are well suited to local condition
II properly laid The return to the distillate pave
| ments was virtually forced upon the Commission
ers by the clause in the appropriation act 10
1857, which provided also, under this apprO